1. Field of the Invention
The present invention relates to the field of shipbuilding and, in particular, to a transport facility with a dynamic air cushion.
The transport facility according to the present invention can be used most successfully for high-speed passenger and freight transportation within coastal marine water areas, on rivers and water storage reservoirs, including also in winter time when rivers and lakes are covered with ice, as well as under the conditions of flat-country areas of land practically in any season of the year.
2. Description of the Prior Art
At the present time, in the field of water transport there is a problem of increasing the speed of vessels. The problem is a crucial one for the growth of their efficiency in carrying out passenger or freight transportation operations.
The solution of the above-mentioned problem has led to the development of transport facilities with a dynamic air cushion. The basic characteristic feature of a vessel with a "dynamic" air cushion consists in that it is provided with an air wing having a small aspect ratio and, as a rule, a rectangular configuration in the plan view, and with skegs mounted along the end ribs of the wing. Under the term of a "dynamic" air cushion is implied an air cushion created by a moving flow of air when it is confined within a dome-shaped arch defined by the wing with its trailing-edge flaps lowered down, by the skegs and by the supporting surface (i.e., the water space or ground surface).
The moving flow is developed by an air supercharger mounted in front of the wing and by the incident flow. The differential pressure within the air cushion creates a lifting force which is equal to or exceeds the weight of the vessel even when it is moving at its minimum speed.
As the speed of the transport facility increases, the prevailing role in the formation of the dynamic air cushion goes over to the incident air flow.
The vessels with the dynamic air cushion possess a number of important performance capabilities which improve substantially their efficiency.
The vessel can be operated within shallow water areas, and at those places where the traffic is intensive it allows use of routes passing outside the ships' way without the interference with the movement of the other vessels. The vessel is able to come out of water to a flat-gradient, relatively-even shore or bank for boarding or landing the passengers and for carrying out maintenance--a factor which considerably simplifies its operation, etc.
This high-speed water-based transport facility can fill the gap in such needs of the society not met as yet, such as fast taxi communication between inhabited localities spaced from each other along the coastline, expeditions, water salvaging service, guarding the water boundaries against trespassers, fishery inspection service, etc.
A transport facility is known in the prior art to have an air cushion, such as, for instance, an air cushion ship (see GB Patent No. 2 120 990).
The prior art ship comprises two hulls which have the longitudinal axes thereof parallel to one another. The above-mentioned hulls are interconnected by means of a central wing provided with trailing-edge flaps. Underneath, in between the hulls is a space open on the side of the front edge of the wing.
In order to improve the aerodynamic quality of this ship, and to increase the ratio between the lifting force and the ship's drag, use is made of side wings provided with trailing-edge flaps. Each side wing is installed on the hull closer to the stern than the central wing. In order to ensure stability of the ship when it is in its cruising mode, a tail empennage is arranged to be disposed within the stern portion thereof, the tail empennage consisting of two vertical keels and a horizontal stabilizer connected with the latter. Each of the keels is rigidly connected with one of the hulls. In front of the bow edge of the central wing, a beam is arranged to be disposed which is joined with the hulls and carries two turbo-propeller engines which are capable of being turned angularly relative to the axis perpendicular to the center line plane of the transport facility--a factor which allows one to vary the direction of the propulsion vector of the engines in the vertical plane coinciding with the center line plane of the ship. The bottom of each hull is made rigid, with sharp keeled frames.
When this prior art ship is moving at low speeds, the gas flow created by the turbo-propeller engines is directed into the space open on the side of the front edge of the wing limited from beneath by the surface of water, from above and from behind by the central wings with its trailing-edge flaps lowered, and from the lateral sides by the hulls. Within the above-mentioned space, braking of the gas flow takes place which is accompanied by the growth of pressure upon the lower surface of the central wing so that a lifting force is thus developed. The horizontal constituent of the propulsion vector ensures the translational movement of the ship. The lifting force reduces the draught of the ship. This leads to a reduction in its hydrodynamic drag and to an increase in the speed of the translational movement of the ship.
As soon as the speed of the translational movement of the ship reaches the magnitude at which the lifting force becomes equal to the weight of the ship, its take-off from the water surface takes place. After this, the trailing-edge flaps are returned to their initial positions, thus ensuring the horizontal direction of the propulsion vector for the mode of cruising.
This design embodiment of the ship described above leads to an increase in the relative weight of the construction and to its higher cost because of a large weight of the beam together with the engines arranged to be disposed on it and because of large weight and great power of the drive used for varying the direction of the propulsion vector.
The rigid design of the bottom of each hull of the ship deprives it of an amphibious property, i.e., the capability of this ship to go out of water and move over the land.
A transport facility is known in the prior art to have a dynamic air cushion (See "Shipbuilding" Journal No. 1, January of 1991, "Soodostroeniye" Publishing House, Article "New Generation of Winged Ships" by V. V. Sokolov, Leningrad).
The above-mentioned transport facility comprises a hull which is provided with a wing mounted within the middle portion thereof and having trailing-edge flaps for developing a lifting force. An empennage is disposed within the stern portion thereof to ensure that the transport facility is stable. The tail empennage is of a single-keel type and has a stabilizer fastened to the end rib of the keel. At either end cross-section of the wing a skeg is installed, and the latter is joined rigidly with the wing and made resilient on the side facing the grounds. Elastic pneumatic balloons are mounted stationarily to the skegs and to the hull on the side thereof facing the ground.
In order to ensure propulsion, this transport facility is provided with two air propellers arranged to be disposed symmetrically with respect to the center line plane of the transport facility in front of the bow edge of the wing. Each propeller is installed within a ring attached to the hull. In order to change the direction of the propulsion vector in the vertical plane which is parallel with the center line plane, either of the rings is provided with flaps installed within the zone of the rear edge thereof so that they can be turned angularly relative to their respective axes which are perpendicular to the center line plane. Each of the supports for the shafts rotating the propellers is fastened rigidly to a beam formed by the rings and a connecting member joined with the latter and attached to the hull within the zone of its bow portion. The shafts for rotating the propellers are connected be means of a mechanical transmission to the engines arranged to be disposed on the upper surface of the wing symmetrically relative to the center line plane of the transport facility.
The transport facility described above has an elevated fuel consumption by the engines because of the necessity to increase the propulsion developed by the propellers due to an increase in the aerodynamic drag caused by blowing the flaps and rings over with the air flow.
Further, the presence of the rings, which have the area thereof influenced by external disturbance, such as, for instance, gusts of wind, reduces the longitudinal and course-keeping stability of the transport facility, to retain which it is required to develop the surface of the tail empennage, but this will lead to an increase in the weight of the transport facility.
This prior art transport facility features reduced values of the specific propulsion of the propellers which is defined as the ratio of the propulsion to the power developed by the engines, because of the limitation imposed upon the diameter of the propeller due to the vicinity of the water surface and due to the stationary position of the propeller. The presence of the two-engines on the above-mentioned transport facility reduces the safety of its operation at the cruising speed since if one of the engines fails unexpectedly, an unbalanced torque appears relative to the vertical axis as a result of the propulsion force developed by the working engine--a factor which will lead to an abrupt change in the course of the transport facility.
In addition, the wing of this prior art transport facility has an elevated coefficient of aerodynamic drag and a reduced coefficient of lifting force because the engines are located on it. These engines have a shortcoming of reducing the reliability of operation of the ship when the sea is running high because they are flooded with water. The presence of the pneumatic balloon mounted to the hull increases both the aerodynamic drag and the hydrodynamic drag of the transport facility and reduces the efficient area of the lower surface of the wing on which the lifting force is developed.
The above-mentioned transport facility has a reduced operational reliability because of a possible failure of its propellers in case of running it into objects which it may encounter along the path of its motion.
This prior art transport facility is difficult to be hauled over the land with its engines in nonoperating condition.
Accordingly, there exists a need for developing a transport facility with a dynamic air cushion, in which, due to an appropriate variation in the design of the beam and to a peculiar disposition of the engine with the transmission, there would be ensured an increase in its economical efficiency, weight efficiency factor, and an improvement in the specific propulsion of the propellers.